For example, Japanese unexamined patent application number Sho 56-116064 (1981) and Japanese examined patent application number Hei 4-15953 (1992) describe image recording devices of this type. In these devices, a toner image is formed on an image holding member such as a photoreceptive drum or a dielectric drum by predetermined means and the image formed on the image holding member is transferred to the transfer medium supplied to the contact portion between the image holding member and the pressure roller bearing against it, so the image holding member and the pressure roller are contacted under a pressure of 20 to 200 kg/cm.sup.2 or 18 to 125 kg/cm.
In the above described image recording devices, as a predetermined pressure is applied between the image holding member and the pressure roller, the contact pressure between them is increased when the transfer medium enters the contact portion by an amount approximately corresponding to the thickness of the transfer medium, so when the transfer medium enters the contact portion, the temporary increase of the load causes a variation of torque in the drive means which rotates the image holding member, which causes a temporary non-uniformity in the rotation of the image holding member. Here, the image formation is being continued on the surface of the image holding member by the image-forming means, and if there is a temporary non-uniformity in the rotation of the image holding member, distortion is caused in the partly recorded image, which in turn causes image defects.
To solve this problem, the use of low pressure toner to reduce the contact pressure between the image holding member and the pressure roller and again to reduce the variation of rotation speed of the image holding member when the transfer medium entering has been tried, and as described in Japanese unexamined patent application number Sho 58-40574 (1983), the provision of a flywheel to the image holding member, which reduces the variation of rotation speed of the image holding member, has also been tried.
The above described conventional image recording device, however, has the following problems, that is, if the contact pressure between the image holding member and the pressure roller is reduced and low pressure toner is used, fusion of toner is caused by stress inside the developing device, and if a flywheel is used, it may be possible to prevent image defects, but the device is inevitably made more bulky and heavier.